This invention relates to a method of drying noodles and, more particularly, to a method by which steamed noodles are allowed to expand and dehydrate rapidly within a short time with process air, inert gas (e.g., N.sub.2, He or CO.sub.2) or mixtures thereof that are delivered at high temperature and speed from spray nozzle tubes.
Three well-known drying methods are currently employed in the instant-noodles products and they are by frying, by drying with hot gases and by drying with superheated steam. As for the second drying method which uses hot gases, Japanese Laid-Open Patent Application No. 44260/1977 teaches a process in which steamed noodles prepared by known procedures are treated with hot gases at elevated temperatures of about 150.degree. C. for a short period of time. Since the noodles to be dried by this method are placed in a specified quantity on a net conveyor, even a hot gas heated to as high as about 150.degree. C. is incapable of dehydrating the interior of the noodles although their surface may be dehydrated quickly. If the drying is continued for a sufficient time to completely dehydrate the interior of the noodles, their surface will be scorched.
Japanese Laid-Open Patent Application No. 86642/1979 teaches a method in which a sealed drying chamber is supplied continuously with steamed noodles, which are expanded to foam with a hot gas of high water content that has been heated to 105.degree.-180.degree. C. and which is recirculated for blowing against the strings of noodles at a rate of 2-10 m/sec. This method which uses the recirculating hot gas of high water content will cause smaller degrees of discoloration and scorching than the ordinary drying method using heated gases at high temperatures. On the other hand, the hot gas of high water content is simply circulated within the sealed drying chamber, so the thermal efficiency of the method on steamed. or boiled noodles is far from being satisfactory and, in addition, the high water content of the hot gas permits the noodles to be expanded to foam by a limited degree.
Japanese Patent Publication No. 44731/1979 teaches a process for producing dry noodles which comprises adjusting the water content of steamed or boiled strings of noodles to about 8-25% and treating them with a hot gas steam at about 120.degree.-250.degree. C. for about 5-90 seconds. According to the disclosure in this reference, if the water content of the steamed or boiled strings of noodles is adjusted to more than 25%, their interior is dehydrated insufficiently to achieve quick drying. This would be due to the inefficient contact of the steamed or boiled strings of noodles with the heated gas stream. It is therefore desired to develop a drying method by which heated gases can be applied uniformly not only to the surface but also to the interior of steamed or boiled strings of noodles having a specified thickness while assuring high efficiency to achieve rapid drying of the noodles so that they are expanded to foam within a short period of time. On the other hand, the rapid expansion and foaming of noodles by drying with heated gases at elevated temperatures is said to accelerate the oxidation of flavor, coloring matter, oils and vitamins in the noodles, thereby damaging their characteristic flavor and color, as well as vitamins and other nutrients.